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CSE 163

Geopandas�

Suh Young Choi�

🎶 Listening to: Johnny Cash

💬 Before Class: What is your favorite world flag?

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Announcements

Midterm evaluations have opened!

  • Will be open today (7/24) – Wednesday (7/26)
  • If >70% of the class fills it out, everyone gets an extra day on HW4!
  • Feedback also helps us out a ton!!

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Checkpoint 4 due tonight

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HW4 and LR4 due on Thursday

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Bonus Dataset Finding Activity releases after class—due next Monday (7/31)

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Checking in with the Check-ins

Checkpoint Tokens and Lesson completions now on Canvas

  • Checkpoint Tokens have been automatically applied to the earliest missed checkpoint
  • Double-check that you have the correct number of completed lessons, CTs, and used CTs!

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Key topics for the LRs

  • Will add these to the slides as they are posted on the website
  • Likely won’t spend time going over each one in detail during class

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This Time

  • Geospatial data
  • Using Geopandas

Last Time

  • Magic methods
  • os
  • HW4 concepts

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Geopandas

  • Exactly like pandas, but with some extra features for geo data
  • Types
    • GeoDataFrame
    • GeoSeries

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import geopandas as gpd

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df = gpd.read_file('data_file.shp')

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df.plot(column='some_col', legend=True)

plt.savefig('plot.png')

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Important!

  • .shp should be used to make GeoDataFrames!
  • .csv should be used to make DataFrames!

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import geopandas as gpd

import pandas as pd

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gdf = gpd.read_file('data_file.shp’)

df = pd.read_csv('data.csv’)

# Don’t do this!!

gdf = gpd.read_file('data.csv’)

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zip

  • zip is a helpful built-in function to help you combine lists

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  • Note: zip does not return a list! It returns a generator
    • Can only access the values by iterating over them
    • Can only be used once! Iterating “consumes” the series

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x = [1,2,3]

y = [4,5,6]

zip(x, y)

[(1,4), (2,5), (3,6)]

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Matplotlib

  • Before, we were using a lot of matplotlib stuff blindly
  • Default plots gets plotted on a global figure (think canvas)
    • Multiple plots would overwrite each other
  • You have to do extra work to get more information on the same set of axes.

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ax

fig

fig, ax = plt.subplots(1)

<plot1>(ax=ax)

<plot2>(ax=ax)

fig.savefig('plot.png')

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plot1

plot2

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Hurricane Florence

Demo

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LR topics may include:

  • Geospatial data
  • .zip and converting to Point/geometry
  • Plotting on multiple axes and subplots

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Before Next Time

  • Complete Lesson 16
    • Remember not for points, but do go towards Checkpoint Tokens
  • CP4 due tonight
  • Fill out the midterm evals!
  • Resub cycle closes tomorrow (last day to resubmit HW1)

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Next Time

  • Two special Geopandas functions

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